Physics of Sound Investigation 2, Part 1

1. Physics of SoundInvestigation 2, Part 1 Vibration and Pitch

2. Materials Tongue depressor per pair Door Fiddler (cord with bead and block) Beans Tone Generator with 9-V Battery

3. Overview • Sound comes from a variety of sources • People • Musical Instruments • Machines • Nature • Sound caused by vibrations. • Pitch = high or low sound • Differences in pitch are caused by differences in the rate or frequency. • Small objects vibrate faster than large objects. • The faster the object vibrates, the higher the pitch of the sound.

4. Tuning a Guitar Create vibrations to tune. When pluck strings, it vibrates. Use tuning knobs to adjust the tension on each string. As increase the tension of a string, that string vibrates more rapidly and its pitch goes higher. As decrease the tension of a string, that string vibrates more slowly and its pitch goes down.

5. Review of Investigations • What observations did you make with the _____? • Door fiddle • Tone generator • Long gongs • Tuning forks • What do the following terms mean? • Sound source • Sound receiver • Vibration • Volume

6. Voice • What is the source of the sound of my voice? • Does a person’s voice make vibrations? • Place fingers flat against the front of your throat and feel the vibration as you… • Talk • Sing • Hum

7. Pitch How high or low a sound is High pitched sounds include squeaks and screeches. Low pitched sounds include rumbles and growls. Stand beside desk. Squat low when hear a low pitched sound. Stand tall when hear a high pitched sound. Use tone generator to play various pitches.

8. Tongue Depressor • How to make sounds with the tongue depressor. • Position on your desk so the end sticks out over the edge like a little diving board. • Use the heel of your hand to hold. • Pluck the tip. • Challenge to discover ways to make high and low pitches with the tongue depressor. • How did you make high and low pitched sounds? • Where are the vibrations? • Compare the high and low pitches.

9. Door Fiddle • How could we make high and low pitched sounds? • Use suggestions and have a volunteer play the door fiddler. • Pluck the longest string and look for vibrations. Then, pluck the shortest string. • What pitch do you hear from the long/short string? • What do you see? • Do the 2 strings vibrate the same? • Explanation: • Faster vibrations make higher pitches. • Slower vibrations make lower pitches. • How fast or slow something is vibrating is called the frequency of the vibration.

10. Tone Generator Place the beans on the speaker. Watch the beans as the pitch changes. What do you predict you will see? Set the volume high and slowly turn the pitch dial from low to high. What is pitch? What happens to the vibrations when the pitch changes? Set the pitch high and slowly change the volume dial. What is volume? What happens to the vibrations as the volume increases?

11. Voice • Feel your throat as you make high and low pitched sounds while keeping your volume at a whisper. • What do you feel? • The vibrations should move and feel slower or faster. • Keep the pitch the same as you increase the volume from a whisper to a hum. • What happens to the vibrations? • The vibrations should feel stronger as the volume goes up.

12. Review • Pitch = how high or low a sound is • High frequency = a fast vibration • What happens to the vibrations when the pitch changes? • Fast vibrations produce high pitched sounds. Slow vibrations produce low pitched sounds. • Science story = Highs and Lows

13. The End!!!